ISO/IEC 23091-3:2018 pdf download – Information technology — Coding-independent code points — Part 3: Audio.
6.4 Program loudness level Type: fixed-point or integer value Range: −41 to 0 dB, with a precision of at least 1 dB ProgramLoudness indicates the overall loudness of the corresponding audio program. It should be measured in such a way that if two pieces of content have their loudness normalized using the value of ProgramLoudness, the resulting audio will have consistent loudness. Decoders evaluate this value and apply an appropriate level shift to audio to maintain a consistent loudness of output audio, matched with a user-given target loudness. The ProgramLoudness should be the overall loudness measured in LKFS according to Reference [3]. 6.5 Anchor loudness level Type: fixed-point or integer value Range: −41 to 0 dB, with a precision of at least 1 dB AnchorLoudness indicates the loudness of the anchor elements of the corresponding audio signal (usually the dialog). The method of identifying the anchor elements is chosen by the content author and is out of scope for this document. It should be chosen in such a way that, if two pieces of content have their loudness normalized using the values of AnchorLoudness, the anchor elements of the resulting audio will have consistent loudness. The AnchorLoudness should be the loudness of the anchor content of the program, measured in LKFS according to Reference [3].
6.6 Range of loudness Type: fixed-point or integer value Range: 0 to 90 dB, with a precision of at least 1 dB LoudnessRange indicates the loudness range of the corresponding audio program. It is the loudness difference between the loudest and softest part of that audio program. The loudness of the loudest part is described by LoudnessRangeTop. LoudnessRange is measured in dB according to EBU R 128 and EBU Tech 3342. 6.7 Top of loudness range Type: fixed-point or integer value Range: −41 to 6 dB, with a precision of at least 1 dB LoudnessRangeTop indicates the loudness value of the top of the loudness range described by LoudnessRange of the corresponding audio program. LoudnessRangeTop is measured in LKFS according to EBU R 128 and, EBU Tech 3342. 6.8 Maximum of momentary loudness level Type: fixed-point or integer value Range: −41 to 6 dB, with a precision of at least 1 dB MomentaryLoudnessMax indicates the maximum value of the loudness values obtained from measurements of the corresponding audio program using a 400 ms window. MomentaryLoudnessMax is measured in LKFS as specified in EBU R 128, EBU Tech 3341 and Rec. ITU-R BS.1771-1.
6.9 Maximum of short-term loudness level Type: fixed-point or integer value Range: −41 to 6 dB, with a precision of at least 1 dB ShortTermLoudnessMax indicates the maximum value of the loudness values in LKFS obtained from measurements of the corresponding audio program using a 3 s window. Measurements are specified in EBU R 128, EBU Tech 3341 and Rec. ITU-R BS.1771-1. 6.10 Short-term loudness level Type: fixed-point or integer value Range: −70 to 6 dB, with a precision of at least 1 dB ShortTermLoudness indicates the value of the loudness values in LKFS obtained from measurements of the corresponding audio program using a 3 s window. Measurements are specified in EBU R 128, EBU Tech 3341 and Rec. ITU-R BS.1771-1. The 3 s window shall include the current frame. 6.11 Peak level Type: fixed-point or integer value Range: −41 to 40 dB, with a precision of at least 1 dB SamplePeakLevel indicates the level of the largest magnitude of the corresponding audio program samples. SamplePeakLevel is measured in dB relative to full scale.TruePeakLevel indicates the level of the largest magnitude of the corresponding audio program samples after oversampling. TruePeakLevel is measured in dBTP as specified in Reference [3]. 6.12 Compressor characteristic Type: Unsigned integer, enumeration Range: 0 – 127 DrcCharacteristic indicates the index of a steady-state compressor input-output characteristic. The characteristic describes the compressor gain in dB depending on the compressor input level in dB measured using a 1 kHz sinusoid. The definition of all DRC characteristics is based on a loudness normalized DRC input level of −31 LKFS. A DRC characteristic index value of 0 indicates that the characteristic is undefined or unknown. The DRC characteristic index values 1–6 are defined by the pseudo code in Table 5 and parameters in Table 6. For a steady state input level inLevelDb in dB, the function returns a DRC gain level outGainDb in dB as shown in Figure 7. The loudness normalized DRC input level is called drcInputLoudnessTarget.